A conventional stepping motor is used exclusively to drive a lightweight load. If the conventional stepping motor is so designed as to drive a heavy load, it becomes large in size and hence the inertia thereof increases. In this case, a stepping operation of the motor requires a long time, so that the motor cannot be driven at a high speed. Further, a large electric power is required to start and stop the electric motor upon start and completion of the stepping operation, and hence the energy efficiency is lowed. In addition, if a stepping angle is set to a small value to enhance the precision of positioning in the conventional DC motor, the motor output torque is lowered.